When Dallas Police Chief David Brown announced Friday that a bomb-carrying robot had killed a suspect in the police shootings, the news startled law-enforcement experts who said it may be a first.

"We were very curious about how it was used,"said Alex del Carmen, executive director of the school of criminology, criminal justice and strategic studies at Tarleton State University in Stephenville. "This marked a historical moment in the new methods that are used by law enforcement agencies."

Brown's description of what happened Thursday night was terse:

"We saw no other option but to use our bomb robot and place a device on its extension for it to detonate where the suspect was. Other options would have exposed our officers to grave danger," Brown said. "The suspect is deceased as a result of the detonating of the bomb."

Del Carmen said he's never heard of another suspect being killed by a police robot in the United States. Even the nonlethal use of police robots as weapons is still very unusual, he said.

"It has become a new method for law enforcement to minimize the exposure of police officers when all other options have been considered," he said.

Weaponized robotics remains a rare area of police expertise, he said.

Del Carmen said he'd heard of weaponized robots being used in other countries, both as a military tool and by some law enforcement agencies. That is relatively recent, he said. What's not unusual is that a technique used by the military gets picked up by American police departments.

"What's used in the field overseas becomes a tool of choice for domestic law enforcement," he said.

Other experts on robots agreed with del Carmen's assessment. Peter W. Singer, of the New America Foundation, told The Associated Press that the killing of a suspect in Thursday night's fatal shooting of five officers is the first instance he's aware of in which a robot has been used lethally by police.

On his Twitter account, Singer described the use of robots by American soldiers in Iraq. Those examples, he tweeted, were jury-rigged and improvised: explosives taped onto a small robot.

But some robots used by American police offer built-in options that go beyond cameras and water cannons to disable bombs.

In November 2014, for example, the Albuquerque police department used its robot to help flush out a suspect in a hotel room. From the department's monthly activity report: "The Bomb Squad robot was able to deploy chemical munitions into the subject's motel room, which led to the subject's surrender."

"Northrop Grumman's Remotec ANDROS F6 robot, for example, can be outfitted with an X-ray to look for explosive material, or a "disruptor" to safely detonate bombs. But it can also be fitted with a pepper-spray dispenser, a tear-gas launcher, and even a shotgun."

The history of remote-controlled land weaponry goes back at least to World War II, when the Soviet Union and Germany packed radio remote controls into devices that could shoot or blow up.

The first "bomb robot" was developed in the early 1970s to deal with car bombs in Northern Ireland, cobbled together by retired British Army Lt. Col. Peter" Miller using a motorized wheelbarrow. All the first devices could do is attach a tow hook to a booby-trapped car. But that allowed the British Army to pull the car to a location where it could be blown up safely.

In the U.S., law enforcement agencies started using robots widely in the 1990s. These days, they range from the size of a go-kart to small enough to literally be tossed through a window. Some are little more than a camera on wheels. But others, like the Andros, can carry a range of probes, tools and projectile launchers of various sizes.

These are some of the options offered in the Northrop Grumman catalog for the Remotec robots.

The cost of a police robot can range from tens of thousands to hundreds of thousands of dollars.

Dallas police have not identified the kind of robot used Thursday night, nor whether the explosive was improvised or something the department had long planned for an emergency.

Now that one police agency has used a robot in such a public way, others are likely to consider doing the same if the situation appears to justify it, said Robert Latiff, a retired U.S. Air Force major-general who now teaches about the ethics of emerging weapons technologies at the University of Notre Dame.

From his perspective, Dallas' use of the robot looks to have been a smart reaction to a very difficult scenario.

"That crossed a line," he said of the Dallas strategy. "It may be a good line, but it's one that others may be crossing with more frequency."

A Dallas police officer runs with his gun drawn during the chaos that followed Thursday night's deadly downtown shootings. (G.J. McCarthy/Staff Photographer)

Dallas police responded after shots were fired during a march and rally in downtown Dallas on Thursday night. (Smiley N. Pool/Staff Photographer)

A mother covers her children as Dallas police respond to shots being fired during a protest over recent fatal shootings by police in Louisiana and Minnesota, Thursday, July 7, 2016, in Dallas. Maria R. Olivas/Special Contributor

A Dallas Fire Rescue truck moves through an intersection into an area blocked off to the public as police go through downtown Dallas searching for suspects in the shooting of multiple police officers after shots were fired at a Black Live Matter rally on Thursday, July 7, 2016. Smiley N. Pool/Staff Photographer

(The Dallas Morning News)

Dallas police respond after shots were fired during a protest over recent fatal shootings by police in Louisiana and Minnesota, Thursday, July 7, 2016, in Dallas. Snipers opened fire on police officers during protests; five officers were killed. Maria R. Olivas/Special Contributor

Dallas police officers crouch behind police vehicles at at the intersection of South Lamar and Jackson streets after a shooting during what had been a peaceful rally and march on Thursday, July 7 in downtown Dallas, Texas. Ashley Landis/Staff Photographer

(The Dallas Morning News)

Silhouettes of law enforcement officers are seen in a parking garage in downtown Dallas in the early morning hours of Friday, July 8, 2016. Smiley N. Pool/Staff Photographer

(The Dallas Morning News)

Protestors react after gunmen shot 11 people during a Black Lives Matter protest on Thursday, July 7, 2016 at the intersection of S Lamar and Jackson St in Dallas, Texas. Ashley Landis/Staff Photographer

(The Dallas Morning News)

A mother tries to calm her daughter as Dallas police respond to shots being fired during a protest over recent fatal shootings by police in Louisiana and Minnesota,Thursday, July 7, 2016, in Dallas. Snipers opened fire on police officers during protests; several officers were killed, police said. (Maria R. Olivas/The Dallas Morning News via AP)

A Dallas Area Rapid Transit police officer receives comfort at the Baylor University Hospital emergency room entrance Thursday, July 7, 2016, in Dallas. Police say one rapid-transit officer has been killed and three injured when gunfire erupted during a protest in downtown Dallas over recent fatal shootings by police in Louisiana and Minnesota. (Ting Shen/The Dallas Morning News via AP)

Dallas Police SWAT team members walk a second story floor at El Centro College following a deadly shooting Friday, July 7, 2016 in Dallas. As a Black Lives Matter protest wound down, a gunman opened fire, shooting 11 police officers, killing five of them. (G.J. McCarthy/The Dallas Morning News)

(The Dallas Morning News)

A family and reverend are escorted into a secured entrance by Dallas Police officers at Parkland Hospital in Dallas in the early morning of July 8, 2016 after shots were fired at a Black Lives Matter rally in downtown Dallas on Thursday, July 7, 2016. Dallas protestors rallied in the aftermath of the killing of Alton Sterling by police officers in Baton Rouge, La. and Philando Castile, who was killed by police less than 48 hours later in Minnesota. (Rose Baca/The Dallas Morning News)

(Rose Baca, The Dallas Morning News)

Dallas Police officers stand in salute as fallen officers are transported into UT Southwestern vans, presumably to the Medical Examiner, through a secure entrance at Parkland Hospital in Dallas in the early morning of July 8, 2016 after shots were fired at a Black Lives Matter rally in downtown Dallas on Thursday, July 7, 2016. Dallas protestors rallied in the aftermath of the killing of Alton Sterling by police officers in Baton Rouge, La. and Philando Castile, who was killed by police less than 48 hours later in Minnesota. (Rose Baca/The Dallas Morning News)